Semiconductor device

ABSTRACT

A semiconductor device includes an insulating layer formed over a semiconductor substrate, the insulating layer including oxygen, a first wire formed in the insulating layer, and a second wire formed in the insulating layer over the first wire and containing manganese, oxygen, and copper, the second wire having a projection portion formed in the insulating layer and extending downwardly but spaced apart from the first wire.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2008-209121 filed on Aug. 15,2008, the entire contents of which are incorporated herein by reference.

FIELD

An aspect of the embodiments discussed herein is directed to asemiconductor device having a multilayer interconnection structure.

BACKGROUND

In current semiconductor integrated circuit devices, a multilayerinterconnection structure has been used to interconnect amongsemiconductor elements. In ultrafine and ultra high-speed semiconductordevices, in order to reduce the problem of signal delay (RC delay), alow-resistance copper (Cu) pattern is used as a wiring pattern.

In order to form a cupper wire, a so-called damascene method ordual-damascene method has been used. The damascene method is a method offorming a wire in which a Cu layer is buried in a wire groove or a viahole formed in an interlayer insulating layer using chemical mechanicalpolishing (CMP).

When the Cu wire is formed, a diffusion-reducing barrier is formed toreduce the diffusion of Cu atoms into an interlayer insulating layer.For the diffusion-reducing barrier, in general, refractory metals, suchas tantalum (Ta), titanium (Ti), and tungsten (W), and conductivenitrides of the above refractory metals have been used.

However, the above materials have a higher resistivity than that of Cu;hence, in order to further decrease the wiring resistance, the thicknessof the diffusion-reducing barrier may be decreased as small as possible.Accordingly, Japanese Laid-open Patent Publication No. 2007-59660discusses a technique that a Cu—Mn alloy is used instead of thediffusion-reducing barrier. The reason for this is that MnSi_(x)O_(y) isformed in a self-alignment manner at the interface between an interlayerinsulating layer and a Cu wire by a reaction of Mn with O₂ and Si, whichare contained in the interlayer insulating layer, and that Mn oxidesfunction as a diffusion-reducing layer. However, at the interfacebetween the interlayer insulating layer and the Cu wire, when Mn whichis not allowed to react with O₂ contained in the interlayer insulatinglayer dissolves in the Cu wire, the resistance of the Cu wire mayincrease.

SUMMARY

According to an aspect of an embodiment, a semiconductor device includesan insulating layer formed over a semiconductor substrate, theinsulating layer including oxygen, a first wire formed in the insulatinglayer, and a second wire formed in the insulating layer over the firstwire and containing manganese, oxygen, and copper, the second wirehaving a projection portion formed in the insulating layer and extendingdownwardly but spaced apart from the first wire.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view illustrating the structure of a semiconductordevice 50 a according to a first embodiment;

FIG. 1B is a cross-sectional view of the semiconductor device 50 a takenalong the line X-Y illustrated in FIG. 1A;

FIGS. 2A-2B are views each illustrating a method of manufacturing thesemiconductor device 50 a according to the first embodiment;

FIGS. 3A-3B are views each illustrating the method of manufacturing thesemiconductor device 50 a according to the first embodiment;

FIGS. 4A-4B are views each illustrating the method of manufacturing thesemiconductor device 50 a according to the first embodiment;

FIGS. 5A-5B are views each illustrating the method of manufacturing thesemiconductor device 50 a according to the first embodiment;

FIG. 6A is a plan view illustrating the structure of a semiconductordevice 50 b according to a second embodiment;

FIG. 6B is a cross-sectional view of the semiconductor device 50 b takenalong the line X-Y illustrated in FIG. 6A;

FIG. 7A is a plan view illustrating the structure of a semiconductordevice 50 c according to a third embodiment; and

FIG. 7B is a cross-sectional view of the semiconductor device 50 c takenalong the line X-Y illustrated in FIG. 7A.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a first embodiment, a second embodiment, and a thirdembodiment will be described. However, the present technique is notlimited to the embodiments mentioned above.

In the first embodiment, FIGS. 1A to 6B are views illustrating asemiconductor device 50 a and a method of manufacturing the same indetail.

According to the structure of the semiconductor device 50 a of the firstembodiment and to the method of manufacturing the same, a contact areabetween an insulating layer containing oxygen and a second barrier layercontaining Mn may be increased. Hence, Mn may be sufficiently consumedby the formation of Mn oxides at a portion at which the contact areabetween the insulating layer and the second barrier layer is increased,and an increase in resistance of a copper wire may be reduced.

FIGS. 1A and 1B each illustrate the structure of the semiconductordevice 50 a of the first embodiment. FIG. 1A is a plan view of thesemiconductor device 50 a. FIG. 1B is a cross-sectional view taken alongthe line X-Y illustrated in FIG. 1A.

In the semiconductor device 50 a of the first embodiment illustrated inFIG. 1A, a fourth interlayer insulating layer is represented byreference numeral 15 b, second wires (Cu wire) are each represented byreference numeral 19 b, and a third wire is represented by referencenumeral 19 c. The fourth interlayer insulating layer 15 b is formed soas to cover an n-type MOS transistor forming region 30 a and a p-typeMOS transistor forming region 30 b. The fourth interlayer insulatinglayer 15 b is preferably formed of SiO₂. As a material forming theinterlayer insulating layer 15 b, a material is preferably used whichhas a higher resistance against chemical mechanical polishing (CMP) thanthat of a third interlayer insulating layer 14 b which will be describedlater.

The second wires 19 b are formed so as to be partly overlapped with then-type MOS transistor forming the region 30 a and the p-type MOStransistor forming the region 30 b. The second wires 19 b each have anapproximately rectangular shape or an approximately circular shape. Thesecond wires 19 b are each preferably formed so as to be electricallyconnected to the n-type MOS transistor forming the region 30 a and thep-type MOS transistor forming the region 30 b. The second wires 19 b arepreferably formed of copper (Cu) which has a low resistivity.

The third wire 19 c is formed in the vicinity of the p-type MOStransistor forming the region 30 b. The third wire 19 c has anapproximately rectangular shape. The third wire 19 c is not electricallyconnected to the n-type MOS transistor forming the region 30 a and thep-type MOS transistor forming the region 30 b. The third wire 19 c ispreferably formed of Cu which has a low resistivity.

In FIG. 1B, the semiconductor device 50 a according to the firstembodiment includes a transistor forming layer 60 and a multilayerinterconnection structure 40 a. The transistor forming layer 60 has then-type MOS transistor forming the region 30 a and the p-type MOStransistor forming the region 30 b. The multilayer interconnectionstructure 40 a has first wires 19 a, the second wires 19 b, and thethird wire 19 c. In addition, in FIG. 1B, constituents similar to thosedescribed with reference to FIG. 1A are designated by the same referencenumerals.

As illustrated in FIG. 1B, a silicon substrate 1 has an n-typeconductivity. An element isolation region 2 has a shallow trenchisolation structure. The n-type MOS transistor forming region 30 a andthe p-type MOS transistor forming region 30 b are defined by the elementisolation region 2.

In the n-type MOS transistor forming region 30 a, a p-type well regionis represented by reference numeral 3 a, a gate insulating film isrepresented by reference numeral 4 a, a gate electrode is represented byreference numeral 5 a, a source region is represented by referencenumeral 7 a, a drain region is represented by reference numeral 8 a, anda silicide layer is represented by reference numeral 9 a.

The p-type well region 3 a is formed by performing ion-implantation of ap-type impurity in the silicon substrate 1. The gate insulating film 4 ais formed on the silicon substrate 1 in the p-type well region 3 a. Thegate electrode 5 a is formed on the silicon substrate 1 with the gateinsulating film 4 a interposed therebetween. Sidewalls 6 a are formed onside walls of the gate electrode 5 a. The sidewalls 6 a may be formedusing silicon oxide (SiO₂) which is an insulating material. The sourceregion 7 a and the drain region 8 a are formed in the p-type well region3 a of the silicon substrate 1. The silicide layers 9 a are provided onthe gate electrode 5 a and in the surface of the silicon substrate 1 inthe source region 7 a and the drain region 8 a.

In the p-type MOS transistor forming region 30 b, an n-type well regionis represented by reference numeral 3 b, a gate insulating film isrepresented by reference numeral 4 b, a gate electrode is represented byreference numeral 5 b, a source region is represented by referencenumeral 7 b, a drain region is represented by reference numeral 8 b, anda silicide layer is represented by reference numeral 9 b.

The n-type well region 3 b is formed by performing ion-implantation ofan n-type impurity in the silicon substrate 1. The gate oxide film 4 bis formed on the silicon substrate 1 in the n-type well region 3 b. Thegate electrode 5 b is formed on the silicon substrate 1 with the gateoxide film 4 b interposed therebetween. Sidewalls 6 b are formed on sidewalls of the gate electrode 5 b. The sidewalls 6 b may be formed usingsilicon oxide (SiO₂) which is an insulating material. The source region7 b and the drain region 8 b are formed in the n-type well region 3 b ofthe silicon substrate 1. The silicide layers 9 b are provided on thegate electrode 5 b and in the surface of the silicon substrate 1 in thesource region 7 b and the drain region 8 b.

A protective layer 11 is formed so as to cover the silicon substrate 1,that is, so as to cover the n-type MOS transistor forming region 30 aand the p-type MOS transistor forming region 30 b on the siliconsubstrate 1. The protective layer 11 is preferably formed, for example,of silicon nitride (SiN). The protective layer 11 is formed to protectthe n-type MOS transistor forming region 30 a and the p-type MOStransistor forming region 30 b.

A first interlayer insulating layer 12 is formed on the protective layer11. The first interlayer insulating layer 12 is preferably formed, forexample, of silicon oxide (SiO₂). The first interlayer insulating layer12 is formed to ensure the insulation between the n-type MOS transistorforming region 30 a and the p-type MOS transistor forming region 30 b.

Openings 24 a are formed to penetrate the protective layer 11 and thefirst interlayer insulating layer 12 so that conductive materials to befilled in the openings 24 a are electrically connected to the gateelectrode 5 a, the source region 7 a, and the drain region 8 a of then-type MOS transistor forming region 30 a. Openings 24 b are formed topenetrate the protective layer 11 and the first interlayer insulatinglayer 12 so that conductive materials to be filled in the openings 24 bare electrically connected to the gate electrode 5 b, the source region7 b, and the drain region 8 b of the p-type MOS transistor formingregion 30 b.

A wire 10 a is formed by burying a conductive material in each opening24 a. A wire 10 b is formed by burying a conductive material in eachopening 24 b. The conductive materials are each preferably formed, forexample, of copper (Cu). In addition, the wire 10 a and thecorresponding opening 24 a are collectively called a contact via, andthe wire 10 b and the corresponding opening 24 b are also collectivelycalled a contact via.

In the multilayer interconnection structure 40 a, a second interlayerinsulating layer is represented by reference numeral 13 a, a thirdinterlayer insulating layer is represented by reference numeral 14 a, afourth interlayer insulating layer is represented by reference numeral15 a, a second interlayer insulating layer is represented by referencenumeral 13 b, a third interlayer insulating layer is represented byreference numeral 14 b, a fourth interlayer insulating layer isrepresented by reference numeral 15 b, a first barrier layer isrepresented by reference numeral 16 a, a second barrier layer isrepresented by reference numeral 17 a, a conductive layer is representedby reference numeral 18 a, the first wire is represented by referencenumeral 19 a, a first barrier layer is represented by reference numeral16 b, a second barrier layer is represented by reference numeral 17 b, aconductive layer is represented by reference numeral 18 b, the secondwire is represented by reference numeral 19 b, a first barrier layer isrepresented by reference numeral 16 c, a second barrier layer isrepresented by reference numeral 17 c, a conductive layer is representedby reference numeral 18 c, the third wire is represented by referencenumeral 19 c, a dummy plug is represented by reference numeral 20 c, andopenings are represented by reference numerals 21 a, 21 b, and 21 c.

The second interlayer insulating layer 13 a is formed on the firstinterlayer insulating layer 12. The second interlayer insulating layer13 a is preferably formed, for example, of silicon carbide (SiC). Thesecond interlayer insulating layer 13 a preferably has a thickness of 15nm to 30 nm. The second interlayer insulating layer 13 a functions as anetching stopper when the openings 21 a, which will be described later,are formed.

The third interlayer insulating layer 14 a is formed on the secondinterlayer insulating layer 13 a. The third interlayer insulating layer14 a is preferably formed, for example, of a low dielectric-constantmaterial having a relative dielectric constant of 3.2 or less. As thelow dielectric-constant material, for example, methylated-hydrogensilsesquoxane (MSQ) having a relative dielectric constant of 2.6, SiLK Kor porous SiLK K, which are the registered trade names of Dow ChemicalCompany, a hydrocarbon-based polymer, or carbon-containing SiO₂ (SiOC)may be preferably used. The third interlayer insulating layer 14 a isused to reduce the problem of signal delay (RC delay) in the multilayerinterconnection structure. The third interlayer insulating layer 14 apreferably has a thickness of 100 nm to 300 nm.

The fourth interlayer insulating layer 15 a is formed on the thirdinterlayer insulating layer 14 a. The fourth interlayer insulating layer15 a is preferably formed, for example, of SiO₂. The fourth interlayerinsulating layer 15 a functions as a protective layer for the thirdinterlayer insulating layer 14 a having a low resistance againstchemical mechanical polishing (CMP). The fourth interlayer insulatinglayer 15 a preferably has a thickness of 15 nm to 30 nm.

The openings 21 a are formed to penetrate the second interlayerinsulating layer 13 a, the third interlayer insulating layer 14 a, andthe fourth interlayer insulating layer 15 a so that conductive materialsto be filled in the openings 21 a are electrically connected to therespective wires 10 a. The first wire 19 a is formed of the conductivelayer 18 a buried in the opening 21 a. The conductive layer 18 a ispreferably formed, for example, of copper (Cu).

The first barrier layer 16 a and the second barrier layer 17 a aresequentially provided between the opening 21 a and the conductive layer18 a. The first barrier layer 16 a is formed at the opening 21 a side.The second barrier layer 17 a is formed at the conductive layer 18 aside.

Since the Cu wire is formed in the opening 21 a, a material whichreduces Cu diffusion and which has superior adhesion to Cu is used forthe first barrier layer 16 a. As the material described above, forexample, titanium (Ti), titanium nitride (TiN), titanium silicidenitride (TiSiN), tungsten (W), tungsten nitride (WN), tantalum (Ta), ortantalum nitride (TaN) may be used. In addition, the first barrier layer16 a may be formed using a laminate including at least two layers of theabove materials. The first barrier layer 16 a preferably has a thicknessof 3 nm to 10 nm. Incidentally, the first barrier layer 16 a may only beformed when it is necessary.

The second barrier layer 17 a is formed between the first barrier layer16 a and the conductive layer 18 a. Since the third interlayerinsulating layer 14 a is formed of SiOC, the fourth interlayerinsulating layer 15 a is formed of SiO₂, and Mn also reacts with Si, thecomposition of Mn-containing oxides forming the second barrier layer 17a is represented by Mn_(x)Si_(y)O_(z)(x:y:z is in the range of 1:1:3 to1:3:5). In addition, the second barrier layer 17 a preferably has athickness of 1 nm to 5 nm.

The second interlayer insulating layer 13 b is formed on the fourthinterlayer insulating layer 15 a. The second interlayer insulating layer13 b is preferably formed, for example, of silicon carbide (SiC) as withthe second interlayer insulating layer 13 a. The second interlayerinsulating layer 13 b preferably has a thickness of 15 nm to 30 nm.

The third interlayer insulating layer 14 b is formed on the secondinterlayer insulating layer 13 b. As with the third interlayerinsulating layer 14 a, the third interlayer insulating layer 14 b ispreferably formed, for example, of a low dielectric-constant materialhaving a relative dielectric constant of 3.2 or less. The thirdinterlayer insulating layer 14 b preferably has a thickness of 100 nm to300 nm.

The fourth interlayer insulating layer 15 b is formed on the thirdinterlayer insulating layer 14 b. As with the fourth interlayerinsulating layer 15 a, the fourth interlayer insulating layer 15 b ispreferably formed, for example, of SiO₂. The fourth interlayerinsulating layer 15 b functions as a protective layer for the thirdinterlayer insulating layer 14 b having a low CMP resistance. The fourthinterlayer insulating layer 15 b preferably has a thickness of 15 nm to30 nm.

The openings 21 b are formed to penetrate the second interlayerinsulating layer 13 b, the third interlayer insulating layer 14 b, andthe fourth interlayer insulating layer 15 b so that conductive materialsto be filled in the openings 21 b are electrically connected to therespective first wires 19 a. The second wire 19 b is formed of theconductive layer 18 b buried in the opening 21 b. The conductive layer18 b is preferably formed, for example, of copper (Cu).

The first barrier layer 16 b and the second barrier layer 17 b aresequentially provided between the opening 21 b and the conductive layer18 b. The first barrier layer 16 b is formed at the opening 21 b side.The second barrier layer 17 b is formed at the conductive layer 18 bside.

Since the Cu wire is formed in the opening 21 b as with the firstbarrier layer 16 a, a material which reduces Cu diffusion and which hassuperior adhesion to Cu is used for the first barrier layer 16 b. Thefirst barrier layer 16 b preferably has a thickness of 3 nm to 10 nm.Incidentally, the first barrier layer 16 b may only be formed when it isnecessary.

As with the second barrier layer 17 a, the second barrier layer 17 b isformed between the first barrier layer 16 b and the conductive layer 18b. Since the third interlayer insulating layer 14 b is formed of SiOC,the fourth interlayer insulating layer 15 b is formed of SiO₂, and Mnalso reacts with Si, the composition of Mn-containing oxides forming thesecond barrier layer 17 b is represented by Mn_(x)Si_(y)O_(z)(x:y:z isin the range of 1:1:3 to 1:3:5). In addition, the second barrier layer17 b preferably has a thickness of 1 nm to 5 nm.

The opening 21 c is formed to penetrate the second interlayer insulatinglayer 13 b, the third interlayer insulating layer 14 b, and the fourthinterlayer insulating layer 15 b. Unlike the opening 21 b, a conductivematerial to be filled in the opening 21 c is not electrically connectedto the first wire 19 a. The third wire 19 c is formed by burying theconductive layer 18 c in the opening 21 c. The conductive layer 18 c ispreferably formed, for example, of copper (Cu).

The dummy plug 20 c is formed in a lower part of the opening 21 c. Thedummy plug 20 c has, for example, a cylindrical shape and is formed tohave a width smaller than that of the opening 21 c. The dummy plug 20 cis formed to increase formation areas of the second interlayerinsulating layer 13 b, the third interlayer insulating layer 14 b, theconductive layer 18 c, and the second barrier layer 17 c. Accordingly,at a portion at which the contact area of the third wire 19 c with thesecond interlayer insulating layer 13 b and the third interlayerinsulating layer 14 b is increased, Mn may be sufficiently consumed bythe formation of Mn oxides. Hence, the resistance of the Cu wire may bemaintained at a low level.

In addition, although the resistivity of Cu is 1.55 Ω·m, the resistivityof Mn is 136 Ω·cm. Hence, it is understood that the resistivity of Mn issignificantly larger than that of Cu. Accordingly, when Mn is notsufficiently consumed between the third wire 19 c and the third andfourth interlayer insulating layers 14 b and 15 b, and when Mn dissolvesin the Cu wire, the resistance of the Cu wire disadvantageouslyincreases.

The first barrier layer 16 c and the second barrier layer 17 c aresequentially provided between the opening 21 c and the conductive layer18 c. The first barrier layer 16 c is formed at the opening 21 c side.The second barrier layer 17 c is formed at the conductive layer 18 cside.

Since the Cu wire is formed in the opening 21 c, a material whichreduces Cu diffusion and which has superior adhesion to Cu is used forthe first barrier layer 16 c as with the first barrier layer 16 b. Thefirst barrier layer 16 c preferably has a thickness of 3 nm to 10 nm.Incidentally, the first barrier layer 16 c may only be formed when it isnecessary.

As with the second barrier layer 17 b, the second barrier layer 17 c isformed between the first barrier layer 16 c and the conductive layer 18c. Since the third interlayer insulating layer 14 b is formed of SiOC,the fourth interlayer insulating layer 15 b is formed of SiO₂, and Mnalso reacts with Si, the composition of Mn-containing oxides forming thesecond barrier layer 17 c is represented by Mn_(x)Si_(y)O_(z)(x:y:z isin the range of 1:1:3 to 1:3:5). In addition, the second barrier layer17 c preferably has a thickness of 1 nm to 5 nm.

FIGS. 2A to 5B are views illustrating a method of manufacturing thesemiconductor device 50 a according to the first embodiment.

FIG. 2A is a view illustrating the state in which a part of themultilayer interconnection structure 40 a is formed on the transistorforming layer 60 illustrated in FIG. 1B.

First, on the first interlayer insulating layer 12 (not illustrated inFIG. 2A) of the transistor forming layer 60, the second interlayerinsulating layer 13 a composed, for example, of SiC having a thicknessof 15 nm to 30 nm is formed by a chemical vapor deposition (CVD) methodor the like. The first interlayer insulating layer 12 functions as anetching stopper when the openings 21 a are formed which will bedescribed later.

Next, the third interlayer insulating layer 14 a composed, for example,of SiOC having a thickness of 100 nm to 300 nm is formed on the secondinterlayer insulating layer 13 a. The fourth interlayer insulating layer15 a is formed using a silane gas (such as trimethylsilane), forexample, by a plasma chemical vapor deposition (CVD) method. The thirdinterlayer insulating layer 14 a is preferably formed, for example, froma low dielectric constant material having a relative dielectric constantof 3.2 or less.

Subsequently, on the third interlayer insulating layer 14 a, the fourthinterlayer insulating layer 15 a is formed, for example, from SiO₂having a thickness of 15 nm to 30 nm. The fourth interlayer insulatinglayer 15 a is formed using a silane gas (such as SiH₂Cl₂, SiH₄, Si₂H₄,or Si₂H₆) by a CVD method or the like. The fourth interlayer insulatinglayer 15 a functions as a protective layer for the third interlayerinsulating layer 14 a having a low CMP resistance.

Next, by a lithography operation and an etching operation, the openings21 a are formed which penetrate the fourth interlayer insulating layer15 a, the third interlayer insulating layer 14 a, and the secondinterlayer insulating layer 13 a and which communicate with the wires 10a and 10 b (not illustrated in FIG. 2A). The fourth interlayerinsulating layer 15 a is etched, for example, by a reactive ion etching(RIE) method using a C₄F₆/Ar/O₂ mixed gas including C₄F₆ which is afluorine-containing gas. The third interlayer insulating layer 14 a isetched, for example, by an RIE method. The second interlayer insulatinglayer 13 a is etched, for example, by an RIE method using a CH₂F₂/N₂/O₂mixed gas including CH₂F₂ which is a fluorine-containing gas. For thisetching, the chamber temperature is set to room temperature or the like,and the gas flow rates are set, for example, to 10 to 35 sccm for CH₂F₂,50 to 100 sccm for N₂, and 15 to 40 sccm for O₂.

Subsequently, for example, by a physical vapor deposition (PVD) method,such as a sputtering method, the first barrier layer 16 a composed, forexample, of Ta having a thickness of 2 nm to 5 nm is formed. Since theCu wire is formed in the opening 21 a, a material which reduces Cudiffusion and which has superior adhesion to Cu is used for the firstbarrier layer 16 a. Incidentally, the first barrier layer 16 a may onlybe formed when it is necessary.

Next, a CuMn alloy layer (not illustrated) composed, for example, of analloy of Cu and manganese (Mn) having a thickness of 5 nm to 30 nm isformed so as to cover an inside wall of the opening 21 a provided withthe first barrier layer 16 a. The CuMn alloy layer contains 0.2 to 1.0atomic percent of Mn atoms and preferably contains 0.5 atomic percent orless thereof. Besides the CuMn alloy layer, a layer composed of amixture containing Mn in Cu may also be used. In addition, when the CuMnalloy layer reacts, the second barrier layer 17 a which will bedescribed later is formed, and hence the CuMn alloy layer may not beillustrated in FIG. 2A. However, in a manufacturing process which willbe described later, the CuMn alloy layer is illustrated.

Next, in a subsequent operation, by a heat treatment performed after theconductive layer 18 a is buried in the opening 21 a, before Cu isdiffused to the second interlayer insulating layer 13 a, the thirdinterlayer insulating layer 14 a, and the fourth interlayer insulatinglayer 15 a, which are exposed to the side wall of the opening 21 a, Mnis diffused to the second interlayer insulating layer 13 a, the thirdinterlayer insulating layer 14 a, and the fourth interlayer insulatinglayer 15 a. In addition, since Mn is allowed to react with oxygencontained in the third interlayer insulating layer 14 a and the fourthinterlayer insulating layer 15 a, the second barrier layer 17 a composedof Mn-containing oxides is formed.

In the operation described above, although Mn is used as a metalmaterial forming the alloy layer other than Cu, when a metal material isavailable which has a higher diffusion rate in Cu that that of Cu, andwhose oxide has a Cu diffusion-reducing effect and superior adhesion toCu, the above metal material may also be used as well as Mn. As themetal material described above, for example, besides Mn, niobium (Nb),zirconium (Zr), chromium (Cr), vanadium (V), yttrium (Y), technetium(Tc), or rhenium (Re) may be mentioned.

Since the CuMn alloy layer also functions as a seed layer ofelectrolytic plating, the thickness thereof is controlled to anappropriate value to form a buried wire in accordance with the wiredimension. In this embodiment, a CuMn alloy layer having a thickness,for example, of 5 nm to 30 nm is formed.

In this operation, the second barrier layer 17 a is formed so as tocover the side wall of the opening 21 a. However, since Mn in the secondbarrier layer 17 a is diffused by a subsequent heat treatment and isallowed to react with oxygen in the third interlayer insulating layer 14a and the fourth interlayer insulating layer 15 a, a CuMn alloy layerincluding Mn-containing oxides is formed; hence, the CuMn alloy layercovering the inside wall of the opening 21 a may not have a uniformthickness.

Next, by an electrolytic plating method, the conductive layer 18 acomposed of Cu having a thickness of 0.5 μm to 2.0 μm is deposited so asto be buried in the opening 21 a. In this embodiment, although theconductive layer 18 a composed of Cu is formed, the conductive layer 18a may be an alloy layer composed of Cu and a metal other than Cu, and asthe metal other than Cu, a material is used which does not increase theresistance of a wire even when it is contained in Cu.

Subsequently, a heat treatment is performed at 100 to 250° C. for 1 to60 minutes. By this heat treatment, Mn is diffused from the CuMn alloylayer and is allowed to react with oxygen contained in the thirdinterlayer insulating layer 14 a and the fourth interlayer insulatinglayer 15 a exposed to the side wall of the opening 21 a. In addition,the second barrier layer 17 a composed of Mn-containing oxides is formedto have a thickness of 1 nm to 5 nm on the side wall of the opening 21 aprovided with the first barrier layer 16 a.

Next, for example, by a CMP method, the first barrier layer 16 a, thesecond barrier layer 17 a, and the conductive layer 18 a are partlyremoved approximately to the middle of the fourth interlayer insulatinglayer 15 a by polishing, so that the first wire 19 a composed of Cu isformed in the opening 21 a.

FIG. 2B is a view illustrating the state in which the second interlayerinsulating layer 13 b, the third interlayer insulating layer 14 b, andthe fourth interlayer insulating layer 15 b are sequentially formed inthat order on the fourth interlayer insulating layer 15 a.

First, as in the case illustrated in FIG. 2A, the second interlayerinsulating layer 13 b composed, for example, of SiC having a thicknessof 15 nm to 30 nm is formed on the fourth interlayer insulating layer 15a (not illustrated in the figure) by a CVD method or the like. Thefourth interlayer insulating layer 15 a functions as an etching stopperwhen the openings 21 b and 21 c are formed which will be describedlater.

Subsequently, as in the case illustrated in FIG. 2A, the thirdinterlayer insulating layer 14 b composed, for example, of SiOC having athickness of 100 nm to 300 nm is formed on the second interlayerinsulating layer 13 b by a plasma CVD method or the like.

Next, the fourth interlayer insulating layer 15 b composed, for example,of SiO₂ having a thickness of 15 nm to 30 nm is formed on the thirdinterlayer insulating layer 14 b by a CVD method or the like.

FIG. 3A is a view illustrating the state in which openings 21 g areformed by a lithography operation and an etching operation whichpenetrate the fourth interlayer insulating layer 15 b and which eachhave a grooved shape in the third interlayer insulating layer 14 b.

As in the case illustrated in FIG. 2A, the fourth interlayer insulatinglayer 15 b is etched, for example, by an RIE method using a C₄F₆/Ar/O₂mixed gas including C₄F₆ which is a fluorine-containing gas.

As in the case illustrated in FIG. 2A, the third interlayer insulatinglayer 14 b is etched, for example, by an RIE method. By these etchingoperations, the openings 21 g are formed which penetrate the fourthinterlayer insulating layer 15 b and which each have a grooved shape inthe third interlayer insulating layer 14 b.

FIG. 3B is a view illustrating the state in which the openings 21 b and21 c are formed by a lithography operation and an etching operationwhich penetrate the fourth interlayer insulating layer 15 b and whicheach have a via shape in the third interlayer insulating layer 14 b.

As in the case illustrated in FIG. 2A, the fourth interlayer insulatinglayer 15 b is etched, for example, by an RIE method using a C₄F₆/Ar/O₂mixed gas including C₄F₆ which is a fluorine-containing gas.

As in the case illustrated in FIG. 2A, the third interlayer insulatinglayer 14 b is etched, for example, by an RIE method. By this etchingoperation, the third interlayer insulating layer 14 b located under theopenings 21 g is etched. By this etching operation, the secondinterlayer insulating layer 13 b is exposed at the bottom of theopenings 21 b and 21 c.

The second interlayer insulating layer 13 b is etched, for example, byan RIE method using a CH₂F₂/N₂/O₂ mixed gas including CH₂F₂ which is afluorine-containing gas. For this etching, the chamber temperature isset to room temperature or the like, and the gas flow rates are set, forexample, to 10 to 35 sccm for CH₂F₂, 50 to 100 sccm for N₂, and 15 to 40sccm for O₂. By this etching operation, the via-shaped openings 21 b and21 c are formed in the third interlayer insulating layer 14 b and thesecond interlayer insulating layer 13 b.

The opening 21 b is formed so that a conductive material to be filled inthe opening 21 b is electrically connected to the first wire 19 a. Onthe other hand, the opening 21 c is formed on the fourth interlayerinsulating layer 15 a under which the first wire 19 a is not provided.That is, in the opening 21 c, the third wire 19 c is formed which willbe described later. The width of the via shape is not particularlylimited. Since it is intended to increase the surface area of theopening, a width smaller than that of the opening 21 g is preferable.

FIG. 4A is a view illustrating the state in which a first barrier layer16 d composed, for example, of Ta having a thickness of 3 nm to 10 nm isformed, for example, by a PVD method, such as a sputtering method, so asto cover the openings 21 g, 21 b, and 21 c, and the fourth interlayerinsulating layer 15 b. Since the Cu wire is formed in the openings 21 g,21 b, and 21 c, as in the case of the first barrier layer 16 a, amaterial which reduces Cu diffusion and which has superior adhesion toCu is used for the first barrier layer 16 d. Incidentally, the firstbarrier layer 16 d may only be formed when it is necessary.

FIG. 4B is a view illustrating the state in which while the firstbarrier layer 16 d covers inside walls of the openings 21 g, 21 b, and21 c, a CuMn alloy layer 17 g composed, for example, of an alloy of Cuand manganese (Mn) having a thickness of 5 nm to 30 nm is formed. Sincethe CuMn alloy layer 17 g also functions as a seed layer of electrolyticplating which will be described later, the thickness thereof iscontrolled to an appropriate value to form a buried wire in accordancewith the wire dimension. In this embodiment, a CuMn alloy layer having athickness of 5 nm to 30 nm is formed. The CuMn alloy layer contains 0.2to 1.0 atomic percent of Mn atoms and preferably contains 0.5 atomicpercent or less. In addition, as the CuMn alloy layer 17 g, a layercomposed of a mixture including Cu and Mn may also be used as well asthe alloy.

In addition, since the surface area of the CuMn alloy layer 17 g isincreased by the presence of the openings 21 g, 21 b, and 21 c, the CuMnalloy layer 17 g formed to cover the openings 21 g, 21 b, and 21 c has asmall thickness as compared to that of the CuMn alloy layer which isformed to cover the openings 21 a by a sputtering method.

In this operation, the second barrier layer 17 a is formed so as tocover the side walls of the openings 21 g, 21 b, and 21 c. However, in asubsequent operation, since Mn in the second barrier layer 17 a isdiffused by a heat treatment and is allowed to react with oxygen in thethird interlayer insulating layer 14 b and the fourth interlayerinsulating layer 15 b, a CuMn alloy layer including Mn-containing oxidesis formed; hence the CuMn alloy layer covering the inside walls of theopenings 21 g, 21 b, and 21 c may not have a uniform thickness.

In addition, since the opening 21 c is formed, the CuMn alloy layer 17 gmay be formed to have a small thickness as compared to that obtainedwhen the opening 21 c is not formed, that is, when the surface area ofthe opening is not increased. The total amount of the CuMn alloy layersputtered on the inside walls of the openings 21 g, 21 b, and 21 c isconstant in one sputtering operation. Hence, when the surface area, thatis, sputtered area, is large, the thickness of the CuMn alloy layer 17 gformed by sputtering may be decreased.

FIG. 5A is a view illustrating the state in which a conductive layer 18d composed of Cu having a thickness of 0.5 μm to 2.0 μm is deposited byan electrolytic plating method so as to be buried in the openings 21 g,21 b, and 21 c. In this embodiment, the conductive layer 18 d composedof Cu is formed; however, the conductive layer 18 d may be an alloylayer including Cu and a metal other than Cu, and as the metal otherthan Cu, a material is used which does not increase the resistance of awire even when it is contained in Cu.

Next, a heat treatment is performed at 100 to 250° C. for 1 to 60minutes. By the heat treatment performed after the conductive layer 18 dis buried in the openings 21 g, 21 b, and 21 c, before Cu is diffused tothe second interlayer insulating layer 13 b, the third interlayerinsulating layer 14 b, and the fourth interlayer insulating layer 15 bexposed to the side walls of the openings 21 g, 21 b, and 21 c, Mn isdiffused to the second interlayer insulating layer 13 b, the thirdinterlayer insulating layer 14 b, and the fourth interlayer insulatinglayer 15 b. Subsequently, Mn is allowed to react with oxygen in thethird interlayer insulating layer 14 b and the fourth interlayerinsulating layer 15 b, and a second barrier layer 17 h composed ofMn-containing oxides is formed.

In addition, by this heat treatment, Mn is diffused from the CuMn alloylayer 17 g and is allowed to react with oxygen in the third interlayerinsulating layer 14 b and the fourth interlayer insulating layer 15 bexposed to the side walls of the openings 21 g, 21 b, and 21 c.Subsequently, the second barrier layer 17 h composed of Mn-containingoxides is formed on the side walls of the openings 21 g, 21 b, and 21 ceach provided with the first barrier layer 16 d to have a thickness of 1nm to 5 nm. In this embodiment, since the third interlayer insulatinglayer 14 b is formed of SiOC, the fourth interlayer insulating layer 15b is formed of SiO₂, and Mn also reacts with Si, the composition of theMn-containing oxides forming the second barrier layer 17 h isrepresented by Mn_(x)Si_(y)O_(z) (x:y:z is 1:1:3 to 1:3:5).

In this case, since the CuMn alloy layer 17 g having a small thicknessis formed as described above, the ratio of Mn of the CuMn alloy layer 17g forming the second barrier layer 17 h on the side walls of theopenings 21 g, 21 b, and 21 c is large than that of Mn dissolved in Cu.Hence, an increase in resistance of the Cu wire caused by dissolution ofMn in the conductive layer 18 d may be suppressed.

FIG. 5B is a view illustrating the case in which, for example, by a CMPmethod, the first barrier layer 16 d, the second barrier layer 17 h, andthe conductive layer 18 d are partly removed approximately to the middleof the fourth interlayer insulating layer 15 b by polishing, so that thesecond wire 19 b composed of Cu is formed in the opening 21 b, and thethird wire 19 c composed of Cu is formed in the opening 21 c. Theoperations described above with reference to FIGS. 2B to 5B arerepeatedly performed, so that the semiconductor device 50 a includingthe multilayer interconnection structure 40 a is formed.

According to the semiconductor device 50 a of the first embodiment, thecontact area between the insulating layers containing oxygen and thesecond barrier layer containing Mn may be increased. Hence, Mn may besufficiently consumed by the formation of Mn oxides at a portion atwhich the contact area between the insulating layers and the secondbarrier layer is increased. As a result, an increase in resistance ofthe copper wire may be reduced.

In the second embodiment, FIGS. 6A and 6B are views each illustratingthe structure of a semiconductor device 50 b having a multilayerinterconnection structure 40 b. In the second embodiment, constituentssimilar to those described in the first embodiment will be designated bythe same reference numerals, and a description thereof will be omitted.

FIGS. 6A and 6B each illustrate the structure of the semiconductordevice 50 b of the second embodiment. FIG. 6A is a plan view of thesemiconductor device 50 b. FIG. 6B is a cross-sectional view taken alongthe line X-Y illustrated in FIG. 6A.

As illustrated in FIG. 6A, in the semiconductor device 50 b of thesecond embodiment, reference numeral 15 b indicates a fourth interlayerinsulating layer, reference numeral 19 b indicates a second wire (Cuwire), reference numeral 19 c indicates a third wire, and referencenumeral 19 e indicates a fourth wire.

The fourth wire 19 e has a concavo-convex portion 22 in a planedirection of a Cu wire. The concavo-convex portion 22 is formed toincrease the surface area of the fourth wire 19 e and that of the Cuwire.

As illustrated in FIG. 6B, the semiconductor device 50 b of the secondembodiment has a transistor forming layer 60 and the multilayerinterconnection structure 40 b. The multilayer interconnection structure40 b has first wires 19 a, the second wires 19 b, the third wire 19 c,and the fourth wire 19 e. Constituents illustrated in FIG. 6B similar tothose described with reference to FIG. 6A are designated by the samereference numerals.

The fourth wire 19 e is formed by burying a conductive layer 18 e in anopening 21 e. The opening 21 e is formed by opening a third interlayerinsulating layer 14 b and the fourth interlayer insulating layer 15 b.The opening 21 e is formed so that a conductive material to be filledtherein is not electrically connected to the first wire 19 a. Theconductive layer 18 e is preferably formed, for example, of copper (Cu).

The concavo-convex portion 22 is formed along the periphery of theopening 21 e. The concavo-convex portion 22 is formed to have an X-Ydirection width smaller than the width of the opening 21 e in the X-Ydirection. The concavo-convex portion 22 is formed to increase a contactarea between insulating layers containing oxygen and a second barrierlayer 17 e which will be described below. Hence, as in the firstembodiment, Mn may be sufficiently consumed by the formation of Mnoxides at a portion at which the contact area of the second barrierlayer 17 e with the third interlayer insulating layer 14 b and thefourth interlayer insulating layer 15 b is increased. Accordingly, theresistance of the Cu wire may be maintained at a low level.

A first barrier layer 16 e and the second barrier layer 17 e aresequentially formed between the opening 21 e and the conductive layer 18e. The first barrier layer 16 e is formed at the opening 21 e side. Thesecond barrier layer 17 e is formed at the conductive layer 18 e side.

Since the Cu wire is formed in the opening 21 e, a material whichreduces Cu diffusion and which has superior adhesion to Cu is used forthe first barrier layer 16 e. The first barrier layer 16 e preferablyhas a thickness of 3 nm to 10 nm. Incidentally, the first barrier layer16 e may only be formed when it is necessary.

The second barrier layer 17 e is formed between the first barrier layer16 e and the conductive layer 18 e. Since the third interlayerinsulating layer 14 b is formed of SiOC, the fourth interlayerinsulating layer 15 b is formed of SiO₂, and Mn also reacts with Si, thecomposition of Mn-containing oxides forming the second barrier layer 17e is represented by Mn_(x)Si_(y)O_(z) (x:y:z is 1:1:3 to 1:3:5). Inaddition, the second barrier layer 17 e preferably has a thickness of 1nm to 5 nm.

According to the structure of the semiconductor device 50 b of thesecond embodiment, besides the structure of the semiconductor device 50a of the first embodiment, the fourth wire 19 e having a concavo-convexportion in a plane direction of the Cu wire is formed. Hence, even inthe case in which a dummy plug may not be formed under the Cu wire, thecontact area between the interlayer insulating layers and the secondbarrier layer containing Mn may be increased. Accordingly, Mn may besufficiently consumed by the formation of Mn oxides at a portion atwhich the contact area of the second barrier layer with the insulatinglayers is increased. As a result, the resistance of the Cu wire may bemaintained at a low level.

In the third embodiment, FIGS. 7A and 7B are views each illustrating thestructure of a semiconductor device 50 c having a multilayerinterconnection structure 40 c. In the third embodiment, constituentssimilar to those described in the first embodiment will be designated bythe same reference numerals, and a description thereof will be omitted.

FIGS. 7A and 7B each illustrate the structure of the semiconductordevice 50 c of the third embodiment. FIG. 7A is a plan view of thesemiconductor device 50 c. FIG. 7B is a cross-sectional view taken alongthe line X-Y illustrated in FIG. 7A.

As illustrated in FIG. 7A, in the semiconductor device 50 c of the thirdembodiment, reference numeral 15 b indicates a fourth interlayerinsulating layer, reference numeral 19 b indicates a second wire (Cuwire), reference numeral 19 c indicates a third wire, and referencenumeral 19 f indicates a fifth wire.

Slit portions 23 are formed inside the fifth wire 19 f. The slitportions 23 are formed, for example, of an insulating material such asSiO₂.

However, when the slit portions 23 are formed, since the cross-sectionalarea of the wire is decreased, an increase in wiring resistanceunfavorably occurs. Hence, the rate of decrease in cross-sectional areacaused by the formation of the slit portions 23 may be set lower thanthe rate of increase in resistance caused by Mn intrusion. The slitportions 23 are formed to increase the surface area between theinsulating layer containing oxygen and a second barrier layer, whichwill be described later, in the fifth wire 19 f. For example, the slitportions 23 are preferably formed so as to decrease a 1 μm-wide fifthwire 19 f by approximately 2.5% and so as to decrease a 3 μm-wide fifthwire 19 f by approximately 5%. In addition, the surfaces of the slitportions 23 may be formed inside the fifth wire 19 f. That is, the slitportions 23 may have a grooved shape formed inside the fifth wire 19 f.

As illustrated in FIG. 7B, the semiconductor device 50 c of the thirdembodiment has a transistor forming layer 60 and the multilayerinterconnection structure 40 c. The multilayer interconnection structure40 c has first wires 19 a, the second wires 19 b, the third wire 19 c,and the fifth wire 19 f. In this embodiment, constituents illustrated inFIG. 7B similar to those described with reference to FIG. 7A aredesignated by the same reference numerals.

The fifth wire 19 f is formed by burying a conductive layer 18 f in anopening 21 f. The opening 21 f is formed by opening a third interlayerinsulating layer 14 b and a fourth interlayer insulating layer 15 b. Aconductive material to be filled in the opening 21 f is not electricallyconnected to the first wire 19 a. The conductive layer 18 f ispreferably formed, for example, of copper (Cu).

In the fifth wire 19 f, the slit portions 23 are formed. The slitportions 23 are formed of an insulating material containing oxygen, suchas SiO₂.

However, when the slit portions 23 are formed, since the cross-sectionalarea of the wire is decreased, an increase in wire resistanceunfavorably occurs. Hence, the rate of decrease in cross-sectional areacaused by the formation of the slit portions 23 may be set lower thanthe rate of increase in resistance caused by Mn intrusion. The slitportions 23 are formed to increase the surface area between theinsulating material containing oxygen and a second barrier layer 17 f,which will be described below, in the fifth wire 19 f. For example, theslit portions 23 are preferably formed so as to a decrease a 1 μm-widefifth wire 19 f by approximately 2.5% and so as to decrease a 3 μm-widefifth wire 19 f by approximately 5%.

A first barrier layer 16 f and the second barrier layer 17 f aresequentially formed between the opening 21 f and the conductive layer 18f. The first barrier layer 16 f is formed at the opening 21 f side. Thesecond barrier layer 17 f is formed at the conductive layer 18 f side.

Since the Cu wire is formed in the opening 21 f, a material whichreduces Cu diffusion and which has superior adhesion to Cu is used forthe first barrier layer 16 f. The first barrier layer 16 f preferablyhas a thickness of 3 nm to 10 nm. Incidentally, the first barrier layer16 f may only be formed when it is necessary.

The second barrier layer 17 f is formed between the first barrier layer16 f and the conductive layer 18 f. Since the third interlayerinsulating layer 14 b is formed of SiOC, the fourth interlayerinsulating layer 15 b is formed of SiO₂, and Mn also reacts with Si, thecomposition of Mn-containing oxides forming the second barrier layer 17f is represented by Mn_(x)Si_(y)O_(z) (x:y:z is in the range of 1:1:3 to1:3:5). In addition, the second barrier layer 17 f preferably has athickness of 1 nm to 5 nm.

According to the structure of the semiconductor device 50 c of the thirdembodiment, besides the structure of the semiconductor device 50 a ofthe first embodiment, the slit portions 23 are formed. Hence, even whena dummy plug may not be formed under the Cu wire, the contact areabetween the second barrier layer containing Mn and the insulatingmaterial containing oxygen may be increased. Accordingly, Mn may besufficiently consumed by the formation of Mn oxides at a portion atwhich the contact area of the second barrier layer with the insulatingmaterial is increased. As a result, the resistance of the Cu wire may bemaintained at a low level.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the embodimentand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a illustrating of thesuperiority and inferiority of the embodiment. Although theembodiment(s) of the present invention has (have) been described indetail, it should be understood that the various changes, substitutions,and alterations could be made hereto without departing from the spiritand scope of the invention.

1. A semiconductor device comprising: an insulating layer formed over asemiconductor substrate, the insulating layer including oxygen; a firstwire formed in the insulating layer; and a second wire formed in theinsulating layer over the first wire and containing manganese, oxygen,and copper, the second wire having a projection portion formed in theinsulating layer and extending downwardly but spaced apart from thefirst wire.
 2. The semiconductor device according to claim 1, whereinthe projection portion has a via shape and/or a grooved shape.
 3. Thesemiconductor device according to claim 1, wherein the width of secondwire is greater than the width of the projection portion.
 4. Thesemiconductor device according to claim 1, wherein the width of thesecond wire is not less than 0.5 μm.
 5. A semiconductor devicecomprising: an insulating layer formed over a semiconductor substrate,the insulating layer containing oxygen; a wire formed in the insulatinglayer, the wire containing copper; a structure formed in the wire, thestructure containing oxygen; and an oxide layer formed between the wireand the structure, or between the wire and the insulating layer, theoxide layer containing manganese.
 6. The semiconductor device accordingto claim 5, wherein the structure has a grooved shape.
 7. Thesemiconductor device according to claim 5, wherein the structuresubstantially includes the same substance as the insulating layer.
 8. Amethod of manufacturing a semiconductor device comprising: forming afirst insulating layer over a semiconductor substrate, the insulatinglayer containing oxygen; forming a first wire in the first insulatinglayer; forming a second insulating layer over the first insulating layerand the first wire, the second insulating layer containing oxygen;selectively removing the second insulating layer to form a first grooveover the first insulating layer; selectively removing the secondinsulating layer on the inner wall of the first groove to form a firstopening exposing the first wire formed under the first groove, and asecond opening extending downwardly but spaced apart from the firstwire; forming a first metal layer over the inner wall of the firstgroove, the first opening and the second opening, the first metal layercontaining manganese; forming a second metal layer in the first groove,the first opening and the second opening, the second metal layercontaining copper; and performing a heat treatment to form a barrierlayer between the second metal layer and the second insulating layer,the barrier layer containing manganese oxide.